Ferric Chloride Oxidation Research Articles

Corrosion characteristics of PPY/GO/CuO nano-composite powder reinforced epoxy coatings on IF steel

The present study has been designed to test the corrosion performance of epoxy based nano-composite coatings on Interstitial Free (IF) steel. PPy and PPy nano-composite powders were formed by polymerization of pyrrole using ferric chloride oxidant. PPy nano-composite powders were synthesized including Graphene oxide (GO) and Copper oxide (CuO) nano-particles. Four combinations have been undertaken in this study viz. pure PPy, PPy-GO (PG), PPy-CuO (PC) and PPy-GO-CuO (PGC). SEM/EDS and XRD results validated the uniform embedding of nano-particles in the pyrrole matrix during polymerization. Moreover, TGA analysis has also confirmed the enhancement of thermal stability of PPy with the incorporation of nano-particles. Further, epoxy (EP) powder was loaded with different concentration of synthesized composite powders to optimize the weight percent (wt%) of PPy, GO and CuO for testing the corrosion characteristics. The different coating configurations were applied on IF steel samples and electrochemical & salt spray testing have been conducted. It has been concluded that coating configuration EP/P2G0.5C1.0 has shown maximum corrosion protection efficiency (ηPE) of approximately 99 %. Moreover, other three configurations EP/P2, EP/P2G0.5 and EP/P2C1.0 have also shown noteworthy results of ηPE of 85, 96 and 97 % respectively. SEM images for cross-sectional view of coatings have also confirmed the uniformity of coatings on to the IF steel. The suitability of these synthesized coatings has also been verified via adhesion test evidencing no significant change in adhesive strength.

Conductive polypyrrole: synthesis, characterization, thermal, and electrical properties for different applications

Pyrrole monomer (mPPy) in an aqueous solution was used to create the conductive polymer polypyrrole (a homo-PPy) using a chemical oxidative polymerization process over a period of several hours at room temperature. Ferric chloride (FeCl3) oxidant was used, and sodium dodecyl sulphate (C12H25NaO4S), a surfactant. The produced PPy samples were characterized using a variety of methods, including X-ray diffraction (XRD), the Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), Differential Thermal analysis (DTA), Thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). SEM images revealed that nanoparticles of a homo-PPy with radii of 60–90 nm were well evenly distributed in the structure. The thermal stability and electrical conductivity of homo-PPy nanoparticles were observed to rise with a solvent ethylene glycol. As temperature rises, the conductivity of homo-PPy samples is significantly raised, and electrical conductivities ranging from.0.44 to 2.2 (Ω.m)−1. Results from FTIR and XRD analysis confirmed the structural formation of a homo-polypyrrole during synthesis from pyrrole monomer. Because of their improved electrical conductivity and thermal stability, homo-PPy nanoparticles have potential applications in energy storage, adsorption and contamination elimination, electromagnetic protection, and resistance to corrosion.

Study of the polishing slurry dispersant for chemical mechanical polishing of 304 stainless steel

To further clarify the effect of the polishing slurry dispersant on the chemical mechanical polishing (CMP) performance of 304 stainless steel, a series of tests were carried out. The correlation between the material removal rate (MRR), surface roughness of 304 stainless steel, dispersant composition, and their content was investigated under two kinds of polishing slurry (hydrogen peroxide oxidant and ferric chloride oxidant) conditions. The experimental results indicated that the MRR and surface roughness of 304 stainless steel arrived at the maximum when the content of sodium hexametaphosphate dispersant was 1.2% (wt) under the hydrogen peroxide–oxalic acid polishing slurry condition. The values of MRR and surface roughness were 146 nm/min and 10 nm, respectively. The MRR and surface roughness of 304 stainless also reached the maximum value as the content of the propanetriol dispersant was 1.2% (wt) under the ferric chloride–oxalic acid polishing slurry condition. However, the values of MRR and surface roughness were 457 nm/min and 22 nm, respectively. Therefore, sodium hexametaphosphate was recommended as the dispersant of hydrogen peroxide–oxalic acid polishing, and propanetriol was recommended as the dispersant of ferric chloride–oxalic acid polishing slurry condition, according to the above analysis. This study lays a theoretical foundation for the improvement of 304 stainless steel CMP performance.

Selection on Surfactant in Polishing Slurry for Chemical Mechanical Polishing 304 Stainless Steel

Stainless steel will become one of the main substrate materials for flexible large-scale displays. As the substrate of the flexible displays, the biggest problem of stainless steel is that the surface roughness is too large. It is necessary to polish the surface of stainless steel with ultra-precision. Chemical mechanical polishing (CMP) technology will be one of the most practical processing technologies to make the surface of stainless steel ultra-smooth and damage-free. In this paper, the material removal rate (MRR) and surface roughness were studied based on the hydrogen peroxide oxidant and ferric chloride oxidant with different surfactants in chemical mechanical polishing (CMP) slurry by experiments. The results show that it can obtain the maximum of the MRR and the optimal surface quality when using 0.04 wt% sodium hexadecyl sulfate as the surfactant of the hydrogen peroxide-oxalic acid based polishing slurry and when using 0.2 wt% nonylphenol ethoxylate or 0.8 wt% OP-10 emulsifier as the surfactant of the of ferric chloride-oxalic acid based polishing slurry. The results of this study can provide a reference for further research on the chemical mechanical polishing of stainless steel.

Role of dissolved air flotation (DAF) and liquid ferrate on mitigation of algal organic matter (AOM) during algal bloom events in RO desalination

Harmful Algal Blooms (HABs) are considered a major contributor to membrane biofouling in Seawater Reverse Osmosis (SWRO) desalination plants. The presence of HABs in the raw feed water leads to an increase in membrane fouling rate, increase of chemical consumption, and can cause temporary shutdown of plants. Effective pretreatment can reduce the amount of organic foulants reaching the RO membrane and alleviate the problem of flux decline during RO operation and frequent membrane cleaning using chemicals. This study compared the effect of in-situ generated liquid ferrate and ferric chloride in combination with dissolved air flotation (DAF) as a pretreatment strategy to remove algal cells and algal organic matter (AOM) during algal bloom events. Experiments were performed using a bench-scale DAF unit. HABs conditions were simulated by harvesting AOM from cultivating Chaetoceros affinis (CA) in raw seawater to a concentration of around 10 mg C/L of dissolved organic carbon (DOC). The liquid ferrate was generated in-situ by wet oxidation of ferric chloride in an alkaline media. The best performance was achieved with the combined use of liquid ferrate and DAF, removing up to 100% of algal cells, 99.99% of adenosine tri-phosphate (ATP), and up to 92% of AOM.

Influence of surface morphology and doping of PPy film simultaneously polymerized by vapour phase oxidation on gas sensing

In this work, polypyrrole (PPy) films were directly deposited on Al2O3 substrate by a facile template-free vapour phase polymerization route using ferric chloride (FeCl3) oxidant. Influence of the surface morphology and doping of the PPy structures on the gas sensing performance was investigated. The synthesized PPy films with different morphologies including nanoparticles-cluster, nanofibers-matrix and porous-structure were obtained by simply regulating the utilized FeCl3 solutions in concentration range from 0.01 to 0.06 M. The increase in the used FeCl3 concentration led to a monotonous increase in the doping/oxidant content of the PPy film. Sensing performances of the PPy films were examined by investigating their resistances responding to NH3, NO2, H2, CO and CH4 gases, and relative humidity (11–95% RH) at room temperature (25 °C). All the PPy films presented to have high selectivity and reversibility to NH3 gas. The highest response to NH3 gas and the lowest humidity influence were found for the nanoparticles-cluster PPy film. The fast sensing response times of the PPy films were about 10, 7, 4 and 3 s in order of the used FeCl3 concentrations of 0.01, 0.02, 0.04 and 0.06 M, respectively. The sensing performances at room temperature of the PPy films were suggested to be attributed by both their surface morphology and doping content.

Synthesis and characterization of highly conductive polypyrrole-coated electrospun fibers as antibacterial agents

Abstract Electrically conductive and antibacterial material was prepared via in situ chemical polymerization of polypyrrole on electrospun fibers of Eudragit L-100 and Eudragit L-100/polyethylene oxide, providing an “all-polymer” template for adsorption and removal of Staphylococcus aureus from surfaces. The optimization in the bactericidal activity of resulting wipes depends on type and concentration of oxidizing agent which affects the morphology and electrical properties of resulting material. We report the optimization provided by ferric chloride (oxidant) on bactericidal activity of wipes of Eudragit L-100/polypyrrole electrospun fibers. Promising results for S. aureus removal confirm the potential application of this polymeric material.

Evaporative successive ionic layer adsorption and reaction polymerization of PEDOT: a simple and cost effective technique for binder free supercapacitor electrodes

The present article describes the development of nanostructured poly(3, 4-ethylenedioxythiophene) (PEDOT) thin film supercapacitor electrodes via conventional solution based inexpensive synthetic approach. Here a novel and simple evaporative successive ionic layer adsorption and reaction (ESILAR) method has been employed to polymerize binderless PEDOT thin films on graphite electrode using ferric chloride (FeCl3) oxidant. This method yields PEDOT thin films of good electrochemical performance with high active material loading (∼2.7–8mgcm−2 with specific capacitance in the range of ∼129–165Fg−1) and exhibits a high specific capacitance of 165Fg−1 for 5.3mgcm−2 PEDOT thin film coated electrode in 1M H2SO4 electrolyte. The effects of various number of ESILAR coating cycles were investigated in terms of the structural, morphlogical and electrochemical properties of PEDOT thin film nanostructures. The PEDOT nanostructures deposit as a straightforward freestanding suface structures were easily processable into a supercapacitor electrodes characterized by excellent cycling stability of ∼80–90% of its initial capacitance retaining after 4000 cycles even free from conductive additives and binders. This method provides a useful orientation on the facile and efficient deposition method of PEDOT thin films applicable for the electrochemical energy storage devices.

Conducting polymer coated graphene oxide reinforced C–epoxy composites for enhanced electrical conduction

Enhanced electrical conductivities were achieved in C–epoxy composites by integrating them with conducting polymers (CPs), namely poly pyrrole (PPY), poly(3,4-ethylene dioxythiophene) (PEDOT) and graphene oxide (GO) enwrapped by CPs. By in-situ polymerization of pyrrole or 3,4-ethylenedioxythiophene (EDOT) in the presence of the GO (template), sodium bis(2-ethylhexyl) sulfosuccinate (structure directing agent), ferric chloride (oxidant), the electrically conductive sheets of GO enwrapped CPs were obtained. The formation of CP coating on GO was confirmed by Raman spectroscopy, scanning electron microscopy and thermo gravimetric analysis studies. Different wt% of CP and CP coated GO were added to the epoxy resin and this resin was used to prepare the 2D laminated C–epoxy composites by hand layup method. DC electrical conductivity of the prepared C–epoxy composites were analyzed using current–voltage (I–V) characteristics and impedance measurements. Typical results showed that CP coated GO, at 0.5wt% addition to epoxy imparted highest DC electrical conductivity for C–epoxy composite.

Antithrombotic effects of the effective components group of Xiaoshuantongluo formula in vivo and in vitro

The present study was designed to investigate the antithrombotic effects and underlying mechanisms of the effective components group (ECG) of Xiaoshuantongluo recipe (XECG) and to further verify the rationality and feasibility of ECG-guided methodology in traditional Chinese medicine (TCM) research. The arterial thrombosis model induced by ferric chloride (FeCl3) oxidation and the venous thrombosis model induced by inferior vena cava ligation were established to evaluate the antithrombotic potential of XECG. Our results indicated that XECG significantly prolonged the time to occlusion, activated partial thromboplastin time (APTT), and prothrombin time (PT), and markedly inhibited adenosine diphosphate (ADP)-induced platelet aggregation in the 20% FeCl3-induced arterial thrombosis model. The superoxide dismutase (SOD) activity was significantly increased and the levels of malondialdehyde (MDA) and nitric oxide (NO) were dramatically decreased in the plasma of arterial thrombosis rats after XECG treatment for 12 days. Furthermore, XECG markedly reduced the weight of thrombus formed by inferior vena cava ligation. Additionally, XECG exhibited 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity and protective effect on mitochondrial lipid peroxidation. In summary, XECG played an important role in the prevention of thrombosis through interacting with multiple targets, including inhibition of platelet aggregation and coagulation and repression of oxidative stress. The ECG-guided methodology was validated as a feasible tool in TCM research.

Synthesis and Optical/Electrochemical Properties of Conjugated Polymers with Diphenyl and Thiophene in Main Chain

Two thiophene derivatives 4,4'-di (thiophen-2-yl) biphenyl and 4,4'-di (thiophen-2-yl) -2-nitrobiphenyl ,which were used as monomers for preparing poly (4,4'-di (thiophen-2-yl) biphenyl) (DPBT) and poly (4,4'-di (thiophen-2-yl)-2-nitrobiphenyl) (DPNT) by ferric chloride oxidation polymerization, were synthesized via Suzuki reaction with 4,4'-dibromobiphenyl as the raw material. UV-vis absorption spectra, fluorescence spectra, photoluminescence spectra and electrochemical properties of the polymers were recorded and used for calculating the band-gap (Eg), HOMO orbital energy (EHOMO) and LUMO orbital energy (ELUMO) of the polymers. The calculation results indicated that attaching an electron-withdrawing group such as-NO2to the main chain can lower band-gap and increase the maximum absorption wavelength.

Production of highly conductive textile viscose yarns by chemical vapor deposition technique: a route to continuous process

AbstractAn oxidative chemical vapor deposition (OCVD) process was used to coat flexible textile fiber (viscose) with highly conductive polymer, poly (3,4‐ethylenedioxythiophene) (PEDOT) in presence of ferric (III) chloride (FeCl3) oxidant. OCVD is a solvent free process used to get uniform, thin, and highly conductive polymer layer on different substrates. In this paper, PEDOT coated viscose fibers, prepared under specific conditions, exhibited high conductivity 14.2 S/cm. The effects of polymerization conditions, such as polymerization time, oxidant concentration, dipping time of viscose fiber in oxidant solution, and drying time of oxidant treated viscose fiber, were carefully investigated. Scanning electron microscopy (SEM) and FT‐IR analysis revealed that polymerization of PEDOT on surface of viscose fiber has been taken place and structural analysis showed strong interactions between PEDOT and viscose fiber. Thermogravimetric analysis (TGA) was employed to investigate the amount of PEDOT in PEDOT coated viscose fiber and interaction of PEDOT with viscose fiber. The effect of PEDOT coating on the mechanical properties of the viscose fiber was evaluated by tensile strength testing of the coated fibers.The obtained PEDOT coated viscose fiber having high conductivity, could be used in smart clothing for medical and military applications, heat generation, and solar cell demonstrators. Copyright © 2010 John Wiley & Sons, Ltd.

Synthesis of high performance, conductive PEDOT‐coated polyester yarns by OCVD technique

AbstractProduction of high performance conductive textile yarn fibers for different electronic applications has become a prominent area of many research groups throughout the world. We have used oxidative chemical vapor deposition (OCVD) technique to coat flexible and high strength polyester yarns with conjugated polymer, poly(3,4‐ethylenedioxythiophene) (PEDOT) in presence of ferric (III) chloride (FeCl3) oxidant. OCVD is an efficient solvent free technique used to get uniform, thin, and highly conductive polymer layers on different substrates. In this paper, PEDOT‐coated polyester (PET) yarns were prepared under specific reaction conditions, and the electrical, mechanical and thermal properties were compared to previously studied PEDOT‐coated viscose yarns. Scanning electron microscopy (SEM) and FT‐IR analysis revealed that polymerization of PEDOT on the surface of the polyester yarns has been taken place successfully and structural analysis showed that PEDOT has strong interactions with viscose yarns as compared to PET yarns. The voltage–current (V–I) characteristics showed that PET yarns are more conductive than PEDOT‐coated viscose yarns. The variation in the conductivity of PEDOT‐coated yarns and the heat generation properties during the flow of current through coated yarns for longer period of time, was studied by time–current (t–I) characteristics. Thermogravimeteric analysis (TGA) was employed to investigate the thermal properties and the amount of PEDOT in PEDOT‐coated PET yarns compared to PEDOT‐coated viscose. The effect of PEDOT coating and ferric (III) chloride concentration on the mechanical properties of coated yarns was evaluated by tensile testing. The obtained PEDOT‐coated conductive polyester yarns could be used in smart clothing for medical and military applications. Copyright © 2011 John Wiley & Sons, Ltd.

Catalytic mechanisms of metmyoglobin on the oxidation of lipids in phospholipid liposome model system

The catalytic mechanism of metmyoglobin (metMb) on the development of lipid oxidation in a phospholipid liposome model system was studied. Liposome model system was prepared with metMb solutions (2.0, 1.0, 0.5, and 0.25 mg metMb/mL) containing none, diethylenetriamine pentaacetic acid (DTPA), desferrioxamine (DFO), or ferric chloride and lipid oxidation was determined at 0, 15, 30, 60, and 90 min of incubation at 37 °C. Metmyoglobin catalysed lipid oxidation in the liposome system, but the rate of lipid oxidation decreased as the concentration of metMb increased. The amount of free ionic iron in the liposome solution increased as the concentration of metMb increased, but the rate of metMb degradation was increased as the concentration of metMb decreased. The released free ionic iron was not involved in the lipid oxidation of model system because ferric iron has no catalytic effect without reducing agents. Both DFO and DTPA showed antioxidant effects, but DFO was more efficient than DTPA because of its multifunctional antioxidant ability as an iron and haematin chelator and an electron donor. The antioxidant activity of DTPA in liposome solution containing 0.25 mg metMb/mL was two times greater than that with 2 mg metMb/mL due to the increased prooxidant activity of DTPA-chelatable compounds. It was concluded that ferrylmyoglobin and DTPA-chelatable haematin generated from the interaction of metMb and LOOH, rather than free ionic iron, were the major catalysts in metMb-induced lipid oxidation in phospholipid liposome model system.

Electrical investigation of polythiophene–poly(vinyl acetate) composite films via VTF and impedance spectroscopy

Polythiophene (PTP) and poly (vinyl acetate) (PVAc) composite films were prepared by chemical oxidative polymerization method with FeCl 3 as an oxidant, in methanol at room temperature. Their dc conductivities as a function of temperature (313–358 K) were measured. An attempt has been made to investigate the effect of temperature and concentration of ferric chloride oxidant on the conductivity of polythiophene–poly(vinyl acetate) composite films. For fixed wt% of PVAc, the dc electrical conductivity of the film initially increases with the molar concentration of FeCl 3 and then decreases with the further increase in the concentration of FeCl 3. The temperature dependence of conductivity showed Arrhenius behavior. The conductivity isotherms show VTF behavior which is typical for ion conducting polymers. The Nyquist plot of Z′ vs. Z″ were plotted for frequency range 100 Hz–200 kHz and temperature range of 313–358 K. These plots consist of semicircles for higher temperatures. This suggests Debye type relaxation mechanism. The equivalent circuit consists of parallel combination of bulk resistance R B and bulk capacitance C B. The bulk resistance R B of the samples decreased with increase in temperature.

Ice-Templating Synthesis of Polyaniline Microflakes Stacked by One-Dimensional Nanofibers

In this paper, a facile and environmentally friendly route, an ice-templating method, has been developed to prepare polyaniline (PANI) microflakes stacked by one-dimensional (1D) uniform nanofibers with diameters in the range 22−32 nm. Although the ice-templating method has been used for preparing ultrapure materials with unique structures in recent years, to our knowledge, this is the first report on using the ice-templating method to direct the polymerization of aniline. Platelet-shaped ice crystals with high aspect ratios provide a particularly novel template to microscopically confine PANI microflakes. The concentration of reagents (aniline, H4SiW12O40 doping acid, and ferric chloride oxidant) and the growth mechanism of PANI flakes are investigated in our experiment. The structure and morphology of the PANI microflakes are characterized by Fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD) patterns, energy-dispersive X-ray analysis (EDX), and scanning electron microscopy (SEM). The c...

Facile Synthesis of Hierarchical Polyaniline Nanostructures with Dendritic Nanofibers as Scaffolds

Hierarchical polyaniline nanostructures with branched nanofibers as scaffolds are prepared by a solution method using ferric chloride oxidant without using any organic structure directing reagent or hard template. The synthesis parameters, such as reaction temperature and time, on the morphologies and crystal structures of polyaniline nanomaterials have been investigated. After 24 h of polymerization at 25 °C, the surfaces of polyaniline dendritic nanofibers are decorated with polyaniline nanorods with diameters of 5−20 nm. Increasing the reaction temperature to 60 °C, the polyaniline nanofibers become smoother, longer, and thinner. XRD, TGA, FTIR, and UV−vis analyses confirm that the products are emeraldine salts with good crystallinity. Also, the product polymerized at 60 °C yields higher thermal stability but lower doping level than that fabricated at 25 °C, which may be caused by the higher content of the phenazine-like segment in the product. The growth process has been discussed.

Ionic conductivity in polypyrrole–poly (vinyl acetate) films synthesized by chemical oxidative polymerization method

Polypyrrole (PPy) and poly (vinyl acetate) (PVAc) composite thin films were synthesized by chemical oxidative polymerization method with the solution of ferric chloride (FeCl3) oxidant in methanol. Their dc conductivities as a function of temperature (308–383K) were measured. The ionic transference numbers for the PPy–PVAc films, synthesized with different concentration of FeCl3, were determined by dc polarization technique. The transference number for the films prepared with 0.1M and 0.2M concentration of FeCl3 are 0.49 and 0.55, respectively. While for the films prepared with 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1M concentration of FeCl3, the transference number lies between 0.78 and 0.99. The dc electrical conductivity of the films, at room temperature, first increases with concentration of FeCl3 and attains the maximum value (σ=6.17×10−10S/cm) at 0.5M of FeCl3. This increase in ionic conductivity of PPy–PVAc film with FeCl3 may be due to increased the mobility of FeCl4- ions promoted by coordination of FeCl2+ with nitrogen of PPy. However, further increase in concentration of FeCl3, decreases the conductivity of the films. The decreased conductivity may be due to reduced segmental motion of polymer. Conductivity variation with FeCl3 shows the percolative behavior. The temperature dependence of conductivity shows clear cross over from Vogel–Tamman–Fulcher (VTF) to Arrhenius behavior. The cross over from VTF to Arrhenius takes place at different temperatures for the films synthesized with different concentration of FeCl3.

Synthesis of polypyrrole films for the development of ammonia sensor

AbstractIn the present investigation, we have synthesized a polypyrrole films by chemical polymerization technique for the development of ammonia sensor. The polypyrrole films were synthesized in an aqueous acidic medium on glass substrate with mild oxidation of ferric chloride at temperature 29°C. The concentrations (molar) of monomer (pyrrole), oxidant (ferric chloride), and dopant (polyvinyl sulfonate) have been optimized for the uniform and porous surface morphology of the synthesized polypyrrole film. The synthesized films were characterized by scanning electron microscopy, ultraviolet‐visible, and Fourier transforms infrared spectroscopy. Ammonia gas sensing behavior of polypyrrole films was studied by using indigenously developed gas sensing chamber. The synthesized polypyrrole film with optimized process parameters shows excellent and reproducible response to low concentration (100 ppm) of ammonia gas. Copyright © 2007 John Wiley & Sons, Ltd.

Effects of sulfur containing amino acids on iron and nitric oxide stimulated catecholamine oxidation.

Taurine is a free amino acid found in high concentrations in tissues containing catecholamines. The ability of taurine and its metabolic precursors to inhibit or stimulate catecholamine oxidation and subsequent quinone formation was examined. Ferric chloride was used as the catalyzing agent to stimulate L-dopa or norepinephrine oxidation and NO donors were also examined for their actions to stimulate quinone formation. Taurine attenuated iron-stimulated quinone formation from catecholamines suggesting that it may function as an endogenous antioxidant. Several other sulfur-containing amino acids (homocysteic acid, cysteine sulfinic acid and SAM) were found to inhibit catecholamine oxidation. Among other amino acids tested, homocysteine had biphasic effects; attenuating L-dopa oxidation catalyzed by ferric chloride and potentiating norepinephrine's oxidation catalyzed by both ferric chloride and sodium nitroprusside (SNP). Homotaurine and homocysteine (1 or 10 mM) greatly stimulated SNP-induced norepinephrine oxidation. Homotaurine potentiated quinone formation in the presence of ferric iron and this effect was attenuated by desferroxamine. In order to exclude a possible NO/iron interaction in SNP's oxidizing action, SIN-1 chloride, a specific NO-donor, was tested as an oxidizing agent. The failure of desferroxamine or taurine to attenuate SIN-1 oxidation of norepinephrine suggests that peroxynitrite-mediated oxidation was likely the dominant mechanism. Our results show that endogenous sulfur containing amino acids, like taurine, could serve a protective role to reduce cellular damage associated with both NO and metal-stimulated catecholamine oxidation.